Process for making acetylene



1964 E. P. GOFFINET, JR 3,161,695

PROCESS FOR MAKING ACETYLENE Filed May 15, 1960 HYDROCARBON FEED 24 I w 20 50 2s 8 I6 48 38 :2 14m PRODUCT 32 GAS HYDROCARBON 46 FEED l TNVENTOR PRODUCT GAS BY 2 WATER Mgm ATTORNEY EDWARD P. GOFFINET,JR.

United States Patent Ofifice 3,161,695 Patented Dec. 15, 1964 3,161,695 PROCESS FOR MAKING ACETYLENE Edward P. Gotiinet, Jr., Claymont, DeL, assignor to E. I. du Pont de Nemours and Company, Wilmington, DeL, a corporation of Delaware Filed May 13, 1960, Ser. No. 28,982 7 Claims. (Cl. 260-679) This invention relates to a process for making acetylene by the pyrolysis of aliphatic hydrocarbons and more particularly to that pyrolysis process in which the aliphatic hydrocarbon is mixed directly with preformed hot combustion gases.

It has long been known that aliphatic hydrocarbons can be pyrolyzed at high temperatures to yield acetylene and other unsaturated hydrocarbons. Various methods are known for providing the heat required to accomplish the pyrolysis. One well-known method comprises burning a mixture of a fuel gas and oxygen or an oxygen-containing gas to produce a hot combustion gas, mixing such hot combustion gas with the hydrocarbon to be pyrolyzed, passing the resulting mixture through a reaction zone where the pyrolysis takes place, and then quenching the hot mixture of gases. leaving the reaction zone, usually with a spray of water. In this process, all of the heat required for the pyrolysis reaction is added at the start and, since the pyrolysis reaction is strongly endothermic, the

- temperature of the system falls rapidly as the reaction proceeds. In US. Patent 2,343,866 this fall is increased by passing the hydrocarbon feed (which is preheated, but

' still at a lower temperature than the reacting gas) in heat transfer relationship with the reacting gas. In U.S. Patent 2,790,838, the'very rapid mixing of very hot combustion tion temperature necessarily gases with the hydrocarbon feed, followed by spontaneous cooling, is emphasized.- In such systems, the initial reacis excessively high in order to allow forthe rapid loss of heat by the pyrolysis reaction j and the large drop of temperature occurring during the reaction, resulting in' a steep temperature gradient and a wide temperature range in the reaction zone. Under such conditions, the conversion of the hydrocarbon to acetylene is undesirably low, large amounts of carbon oxides are formed at theexpense of the hydrocarbon, and the concentration of acetylene in the product gas is undesirably low which renders it more difiicult to recover the acetylene from the reaction products.

It is an object of this inventionto' provide a new and improved process for making acetylene by the pyrolysis of aliphatic hydrocarbons." Another object'is to provide an improved process for making acetylene by the pyrolysis of aliphatic hydrocarbons, wherein said aliphatic hydrocarbons are mixed with preformed hot combustion gases, so that the pyrolysis is caniedoutover a narrow range of moderate temperatures. A further object is to provide a process of the above character whereby improved conversions of the hydrocarbon to acetylene and much higher concentrations of acetylene in the product gases are obtained. Other objects are to advance the art. Still other objects will appear hereinafter.

The above and other objects'may be accomplished in accord with this invention which comprises the process for continuously forming acetylene by the pyrolysis of an aliphatic hydrocarbon of 1 to 6 carbon atoms which is a member of the group consisting of alkanes and olefins, which comprises mixing the aliphatic hydrocarbon with a hot combustion gas which is completely formed in a combustion zone by the combustion of a combustible gas and about a stoichiometrical proportion of oxygen, continuously passing the mixture through an elongated tubular reaction zone while maintaining the temperature of the gaseous mixture at the exit of the reaction zone at a temperature of from about 1000 C. to about 1600 C.

and maintaining the temperature of the gaseous mix ture throughout the length of the reaction zone at from 800 C. to not more than 250 C. above the exit temperature by employing an initial amount of the combustion gas sutficient to provide a mixture at the entrance to the reaction zone having a temperature within the last mentioned temperature range and supplying additional heat to the gaseous mixture intermediate the length of the reaction zone to replace heat consumed in the pyrolysis reac tion, and quenching the gaseous mixture flowing from the reaction zone.

It has been found that by so carrying out the reaction, that is, by carrying out the reaction at moderate temperatures and maintaining those temperatures within a narrow range by employing only part of the heat required for the pyrolysis at the start of the reaction and adding the rest of the heat during the course of the reaction while avoiding excessively high peak temperatures, there is obtained much better conversions of the hydrocarbon feed to acetylene, much lower conversions of hydrocarbon to carbon oxides, and the product gases contain much higher concentrations of acetylene and much lower concentrations of carbon oxides.

'Ihe aliphatic hydrocarbons to he pyrolyzed will be those conventionally employed for the pyrolytic production of acetylene by the heat from hot combustion gases and usually will be alkanes and olefins of 1 to 6, preferably 2 to 6, carbon atoms. Such hydrocarbons are represented by methane, ethane, propane, butane, pentane, hexane, ethylene, propene, butene, pentene and hexene Those which are liquids at atmospheric temperature preferably will be employed as vapors, usually preheated to above their boiling points.

The combustible gases which are employed as the fuels tor producingthe hot combustion gases may be any of those conventionally employed for producing hot combustion gases for the pyrolysis of aliphatic hydrocarbons to acetylene. They may be defined as those substances which are gases at 25 C. and atmospheric pressure, contain no elements other than hydrogen, carbon and oxygen, and are capable of burning in air. Particularly desirable combustible gases are methane, hydrogen, and carbon monoxide. Another highly desirable combustible gas is the mixture of by-products, obtained by removing acetylene from the pyrolysis products of the present and related processes, which by-product gas consists principally of hydrogen admixed with minor amounts of hydrocarbons and carbon oxides.

The hot combustion gases are completely formed prior to admixture with the hydrocarbon to be pyrolyzed, i.e. by the total combustion of the combustible mixture in a combustion zone sepmatcd from the pyrolysis reaction zone. They will be formed by burning a mixture of the combustible gas with a combustion-supporting gas, such as pure oxygen, air, or other oxygen-containing gas. Preferably, however, the combustion gas will be produced froma mixture of pure hydrogen or by-product gas and pure oxygen because such mixtures yield little or no gas, such as carbon dioxide, to further dilute the acetylene formed. It is preferred to employ a substantially stoichiometrical proportion of oxygen and combustible gas. Some variation (i2%) is allowable. Also, the temperature of the hot combustion gas may, and usually will be, regulated by introducing steam with the combustible mixture, in the manner well known to the art. Preferably, the hot combustion gas will have an initial temperature of from about 2000 C. to about 2200 C.

The hydrocarbon to be pyrolyzed, the combustible gas and the combustion-supporting gas may, if desired, be preheated. However, the hydrocarbon feed should not be preheated above its decomposition temperature and preferably not above 600 C.

The process-usually will be carried out at about atmospheric pressure, but higher or lower pressures may be used if desired. High gas velocities may be used, but are not necessary. Rapid mixing of the hot combustion gas and the hydrocarbon feed is desirable, but not critical.

tus comprises a main combustion zone 10, provided with a burner 12 and connected with an elongated tubular reaction zone 16 through a conical mixing zone 14 where the hot combustion gases are mixed with the hydrocarbon to be pyrolyzed. The conical mixing zone 14 is provided with a plurality of small ports in its outer wall and is surrounded by a distributor 48 connected through inlet pipe 50 to a supply of hydrocarbon feed to be pyrolyzed. As shown, the reaction zone 16 is a cylindrical passage through refractory material 18 which conveniently may be a block of cast refractory alumina. The reaction zone may be lined with a tube of self-bonded silicon carbide, if desired. The refractory material 18 is enclosed within a cylindrical metal shell, provided at each end with water-cooled flanges 20 and 22. Auxiliary combustion zones 24 and 30 provided with burners 26 and 34, re-

spectively, are provided for introducing combustion gases through ports 28 and 32, extending through the refractory material 18 and longitudinally spaced intermediate the length of the reaction zone 16. Desirably,'the ports 28 and 32 will be lined with self-bonded silicon carbide. The exit end of the reacfionzone leads. into. a quenching zone 36, provided with a water spray 38. The quenching zone 36 is in open communication with an entrain-7 ment tank 42 for separating the water from the'product gas. The entrainment tank 42 is providedwith a product gas outlet pipe 44. and a water outlet pipe 46.

The various parts of the apparatus will be constructed of suitable materials which have the strength, physical permanence, and chemical stability required to withstand the temperature and pressure conditions employed, and which are not seriously attacked by the hot gases involved and are free from undesirable catalytic action on the hot, gaseous mixtures, such materials being conventional and well known to those skilled in this art. 'Metals, such as steel, copper, brass and aluminum, are suitable in many places where they are not subjected to destructively high temperatures or are protected by external cooling. For example, in the apparatus of FIGURE 1 as used, the

mixing zone 14 was constructed of brass and the walls of the combustion zones 10, 24 and 30 were constructed of steel and cooled by water-jackets (not shown).

In the operation of the equipment of FIGURE 1 in accord with the process of this invention, a mixture of a combustion gas, e.g. hydrogen, and a combustion-supporting gas, e.g. oxygen, usually containing steam for tempering,-is introduced through the burner 12 and completely burned in the combustion zone 10. The hot combustion gas passesgthrough the conical. mixing zone 14 where it is mixed with the hydrocarbon to be pyrolyzed, introduced through pipe 50 and distributor 48, and the mixture then passes through reaction zone 16. The

ture in the product gases leaving the reaction zone.

Due to the highly endothermic reaction taking place in the reaction zone, the temperature of the reacting mixture tends to rapidly decrease. The rest of the required amount of the combustion gas is formed in the auxiliary zones 24 and 30 and injected through ports 28 and 32 into the reacting mixture in the reaction zone to replace heat consumed in the pyrolysis reaction and to increase the temperature of the reacting mixture up to approximately the temperature of the mixture entering the reaction zone. The amount of combustion gas introduced through ports28 and 32'is controlled or adjusted in accord with the temperature, of the reacting gas mixture at those points so as; to raise the temperature to that desired for eflicient; pyrolysis without raising the temperature of the reacting mixture more than 250 C. above the temperature of the-mixture leaving the reaction zone. With the apparatus shown in FIGURE 1, the amount of combustion gas injected through each of ports 28 and 32 usually will be about 50% of that introduced from the main combustion zone 10 or, about of the total amount of combustion. gas required to complete the pyrolysis. -Thereby,;-the temperature in the reaction zone arated from theses.

-ythrongh pipe; 44, -is then treated in known manner to 30.

,-is-.rnaintained.-within a narrow range ofmoderate temperatures. The reaction products leaving the reaction zone are then quenched in zone 36 and passed through entrainment tank 42 where the quenching water is sep- The product gas, passing out recover the, acetylene. and, if desired, other valuable by products and/or stored for-later treatment or desired use.

While the apparatus of FIGURE 1 is shown with two auxiliary combustion zones 24 and and two ports 28 and32, -,the number; of such auxiliary combustion chamb s. audpor e flutherz uc as with pp p spacingalong thesreacliuu zone, so asto'obtain a narrow r. .rapge; or more .unitorm, temp throughout reaction zone, and further increases inthe desirable 'efiects. Howeven; each additional auxiliary combustion .1 zone. and; port hasesmaller eiieet; andrendersthe equip- 11 ment. more complicated; :and costly. From two to about five auxiliary combustion zones and ports are preferred for ,bestrealizing thefull advantages of the invention,

, andfor practical reasons. fFurthermore, asingle auxiliary combustion zone may be used to supply the hot combus- -.tiongases :for a plurality of spacedports. On the other hand,-. the advantages of this invention are. only partially realized by a single; port instead. of a plurality of spaced ports.

- Alternatively,within the broad aspects of this invention,

. the heat, introduced intermediate the ends of the reaction zone for completing: the pyrolysis and maintaining the narrow range of temperatures-throughout the reaction 'zone, maybe supplied by means other thanthe auxiliary combustion zones and ports. Electrical heating elements, or the like, may be positioned in the reaction zone. The combustionrzone may be formed of a tube of heat conductive refractory material, such as self-bonded silicon carbide, and heated externally as byhot gases, hot liquids,

or electrical heating elements, to provide the additional heat required for operation in accordance with the prinamount of combustion gas formed in combustion zone 10 ciples of this invention.

Referring more particularly to FIGURE 2, the elongated tubular reaction zone 60 is.formed by a cylindrical tube 62 of a suitable heat conductive refractory material, such as self-bonded silicon carbide. Such tube 62 also forms the inner wall of an elongated annular combustion zone 64 surrounding the tube 62, the outer wall of said combustion zone being formed by a boring through a stack of alumina brick 66. This brick structure is enclosed by a metal shell 68 and water-cooled flanges 7t and 72. Two burners 74 are provided at the lower end of the combustion zone 64 near the exit end of the reac tion zone 60. A hydrocarbon feed pipe 76, connected with a supply of hydrocarbon to be pyrolyzed, passes through flange 70 and is aligned coaxially with the reaction tube 62 so as to direct the hydrocarbon feed into the inlet end of the reaction tube. A water spray 78 is provided in a quenching zone 80 at the exit end of the reaction tube.

In operation of the embodiment illustrated in FIGURE 2, a mixture of a combustible gas, e.g. hydrogen, and a combustion-supporting gas, e.g. oxygen, usually contain ing steam for tempering, is introduced through burners 74 and is completely burned in the combustion zone 64 While the burning gases flow along the wall of the reaction tube 62 from near the exit end to the inlet end thereof, giving up part of their heat to the reaction zone and the gaseous mixture flowing through the reaction zone. The

resulting hot combustion gas, after reaching the inlet end of the reaction tube, is mixed with the hydrocarbon to be pyrolyzed, introduced through pipe 76, and said mixture enters the inlet end of the reaction zone, passes down- "Wardly through the reaction zone to its exit end, and then through the quenching zone 80 from which it passes to anentrainment tank providedwith gas and water outlets, like 42, 4 4 and 46, respectively, shown in FIGURE 1. The combustion gas, formed in the combustion chamber 64, vjill belsuflicient to provide all of the heat required to initiate and tocomplete the pyrolysis of the hydrocarbon, andto produce the desired temperature in thejproduct atthe exit end of .the reaction zone, "i.e.' exittemperatures of from about 1000" C. to about 160 0., preferably from about 1100" o; to about 1200* C.-51 400 C. flhrough loss of heat to the reaction tube 62 and its t, nts,the hotcombustion gas is of decreased :temperature'iwhen itreachesIthQzQneotmiXing with the i' d c hf n and "'tempe'raturebf the' gases at the 'end' of. the reaction tube. The heat firom thefburningjgases, which is conf ducted through thewall of the reaction tube, replaces heat opsma lpyrolysisfreaction 'andmaintains the tempera the re'actibn zonewithinfa narrow range :of model temperaturm which afhoftime'jare' more than 250' Cl above'the'exit temperature", Usually,.with exit temperatures of from about 1100 C. to about 1400 C; anda combustible mixture which normally, produces a combustion ga's'having a temperature of from about 2000" C. toabout 22009 'C.,' theinitial temperature at the inlet end of the reaction zone will be from 800 C. to about 1000 C., and-the heat fromthecombustion zone. conducted through the wall ofthe reaction tube will gradually increase theitemperature within the reaction zone was desired exit temperature without at any time exceeding thatiexit temperature.

The equipment and process as above described most s ani n... fpressure. Higherand'lower pressures may be used, if desired. gas velocities will'usually be such that the residence of time of'the gas undergoing pyrolysis in the reaction zone 'will'bejrom about 0.5 to about milliseconds, and preferably from about 1 to about 3'milli- '--.',seconds. 'I'he'mean temperature at which the pyrolysis 'takes placeand the'exit'temperature maybe varied as desired by varyingthe temperatute of the hot combustion Y gas, the ratio thereof tothe hydrocarbon feed, or both. In order to more clearly illustrate this invention, prefFFed modes for carrying it into eifect and the advantageous results to be obtained thereby the following examples are given.

EXAMPLE 1 The apparatus shown'in FIG. 1 is used. The main combustion zone 10 is 2 in. in diameter and 10 in. long. The reaction zone 16 is 1.5 in. in diameter and 20 in. long. The auxiliary water-cooled combustion zones 24 and 30, for introducing additional quantities of combustion gases provides'an initialjreaction temperature of at leastj800 C. but not more 250 C. above the" into the reaction zone, are 12 in. long and are located 6 in. from each end of the react-ion zone.

A mixture of hydrogen at a rate of 11.4 lbs/hr. and oxygen at a rate of 76 lbs./hr., with added steam at a rate of lbs./hr., is introduced through the main burner 12 and burned in the combustion zone 10 while one half these quantities of oxygen, hydrogen, and steam are introduced through each of the auxiliary burners 26 and 34 into combustion zones 24 and 30. The feed stock, consisting of 83 lbs. of propane per hour is introduced through 50 and 48 into the mixing zone 14. All gases are fed at ambient temperature and at pressures giving the stated flow rates and one atmosphere pressure at the exit. The steam is saturated and somewhat above atmospheric pressure. The temperature of the combustion gas (super-heated steam) is about 2000 C. to about 2200 C. in each case. The temperature immediately after mixing with the feed is about 1500 C. and decreases, due to the heat absorbed in the cracking of the propane, to about 1300 C. before the gas reaches the port 28. Here the combustion gas introduced through port 28 raises the temperature to about 1500 C. again and the further reaction taking place lowers it to about 1300 C.

-before it reaches port 32. The same cycle takes place .with the port 32, the temperature of the gas leaving the reaction zone being about 1300f C. The residence time is 3 milliseconds and the maximum gas velocity is'ahout 800 ftapersec. (Sonic velocity at this temperaturmand pressure is about 3000 ft. per see). This gas isthen quenched with a water spray and leaves vthe system at atmospheric pressure. Itcontains, on a dry basis, by

"EXAMPLEZ "L The apparatus shown in FIG. 2 is The cylindrical reaction chamber is 0.5 in. in diameter and 7.5 in. long, with a wall62 of self-bondedsilicon carbide Ma in.

, thick and packed with 4- mesh grains of A1 0 The distance between the outer and inner walls of the combustion chamber 64 is A; in. A'mixture ofoxygen at the rate of 1.08 cu. ftjmin. (4.97 lbs/hr.) and hydrogen at a rate of 2.08 on. ft./min. (0.622 lbs/hr.) is introa y. be at about atmospheric duced through burners 74.inlto. the annular combustion chamber 64 in which it reacts completely; The resulting hot combustion gas, when it reaches the opposite end of the combustion chamber,-is mixed with propane, entering through 76 at the rate of 0.17 cu. fL/min. (1.146 lbs./hr.). All gases are fed at the ambient temperature and at pressures giving the stated flow rates and one atmosphere pressure at the exit. The initial temperature of the combustion .gas is about 2000 C. and its final temperature,

just before mixing with the propane, is about 1200" C. The mixture with the propane is initially about 800 C., increases rapidly the first inch to about1000f C., and then gradually increases to the outlet temperature of about 1160 0., without at any time exceeding 1200 C. The residence time is 1.3 milliseconds and the velocity 470 ft. per sec. At the end of the reaction tube, the

temperature of the reaction product gas is 1160 C. This product gas is then queTnched' with water from noule 78 and passed out through 80 at atmospheric pressure. The composition of the exit gas on a dry basis, by volume, is 19.05% acetylene, 5.5% ethylene, 17.2% methane, 0.14% propylene, 0.63% methyl acetylene,'50.96% hydrogen, 0.27% carbon dioxide and 4.90% carbon monoxide. The conversion to acetylene is 52%.

The following examples are given for purposes of comparison.

EXAMPLE 3 The apparatus employed was similar to that of Example l and FIGURE 1, all of the oxygen and the hymethane,v t7.9%' hydrogen, 9.5%

Y 7 drogen being burned in a Water-cooled combustion zone (like 10 of FIGURE 1) leading to a self-bonded silicon carbide reaction tube 0.5 in. in diameter and 10 in. long, insulated by alumina brick, at the entrance to which tubethe hot combustion gas was mixed with the propane feed, and the gas leaving (the reaction tube was quenched with water as in Example 1.

Hydrogen, at the rate of 3.70 cu. ft./min., was burned .withoxygen, supplied at 1.85 cu. .ft./min., the temperature being controlled by adding steam at the rate of 3.0 cu. lit/min. The hot combustion gas was then mixed with 1.15 cu. ft./min. of propane. The initial temperature of the mixture was about 1900" C. and the exit temperature of the pyrolysis products was about 15 C. -The productv gas contained, by volume on a dry basis, 12.2% acetylene, 5.1% ethylene, 9.8% methane, 57.7% hydrogen; 11.6% carbon monoxide, and 3.4% carbon dioxide.

EXAMPLE 4 The apparatus and procedure of Example 3 was followed, except that there was employed 3.36 cu. ftJmin. .of hydrogen and 1.68 cu. ft./ min. of oxygen. The temperature was about 1800" C. and the exit temperature I was 1400 C. -The product gas contained, by volume on ,a dry'basis, 12.9% acetylene, 12.7% ethylene, 12.9% carbon monoxide, and

'3.5% carbondioxide.

Ihe' resultsjofthe preceding examples are summarized inflthe following Table I; together with, under column A.R.S.,-the results of the best of the experiments reported by Akin, Reid andlSchrader in Chemical Engineering Progress, January 1958, page 41, inwhich propane is pyrolyzedlbym xingit at one point with the hot cornbustion products of propane and oxygen.

, -;'1ALBLEI' Composition of Pyrolysisfias, Percent by Volume .Em pls 1 2 a- 4 ans.

;155. ,.19.0 12.2 {12.9 11.0 4.7 5.5 5.1 12.7 12.2 ,;14.9 17.2 v 9.8 112.9 mi 57.9 51.0 57.7 47.9 37.0 5.7 4.9 11.6 9.5 8.4 0.8 -o. a a4 3.5 is 0 45 The=essentiaLdifierence between the conditions and processes employed in Examples 1 and 2 (representative -0f-this invention) and those employed in the other examples (representative of the prior art) is that in processes of the prior that this invention constitutes a'valuahle advance inand contribution to the art. The embodiments of the invention in whichan exclusive property or privilegeis claimed are as. follow s:

1- The process ,forcontinuously fortningdacetylene by the pyrolysisof an aliphatic hydrocarbon of 1 to6 carbon atoms which is a member. of .the, group consisting iof alkanes and olefins, .which comprises mixing the aliphatic hydrocarbon with a ,hot combustion gasiwhieh is com pletely formedin a combustion'zoneby-xthe combustion of a combustible gas and about a stoichiometrical.proportion of oxygen, continnouslypassing themixture through an elongated tubular reactio'r i zonewhile maintaining the temperature of the, g gaseous {rhixtnre.,atthe ,exit "oi, the

gaseous mixture zone at from 800 combustion gas sufiio enttoprovide the last mentioned, f tionalsheat to the g;

1 pyrolysis 1 reaction, 'a nd ,qu fl i o t iereacti. z'or j. and. o e n whic c mp s t h. otflwmh stt pletely' for medjn, combustioil'zt faeomb ti 'g #Examples land 2 only part of the heatrequired ;for1the pyrolysis introduced at the start of the reaction and the rest of-therequired-amount of heat is introduced during i'the course of the reaction (intermediate the length of the reaction zone) so' that the temperatures throughout,

--the-reaetion zone are moderate and are maintained a narrow-range; whereas in the other examples all of the --heat required is introduced at one time at the start of the reaction and-isfollowed by a steep temperature gradient sothat the reaction takes place over a wide range'of tem- .peratures Such examples show that the process of the present invention gives much higher yields of acetylene and lower yieldsof oxides of carbon and the product 1 gases contain much higher concentrations of acetylene and combustion gas suflicient;

the pyrolysis of an aliphatic do be bifl' a toms which a gm e co trance to the reaction'zon h of the, reaction";zonev amenity n g .7 hwhl t eemh 'fis fim 1. 0m, iwh l' m in ainin d a. sf i of px a me qt ugus rp s ins an qnsa e t bu -r temperature ofjt as qvamimfe a the exit of h reaction zone at a temperature of about 6 e. an. 1

as mt rwl ba wheat from 800 'tofnot? exit temperature by j t' an mone? it threesome h 6 l h I 51 h :IQ Q'iQ reffl a 250? Cjabov'e-tlie amount of the V V ovide afmixture atthfehtrance to the reaction zone a temperature the last mentioned-temperaifiir'frange andfintr'oducing into the'reaction zoneata of spaced intermediate its length-additional ahaounts hf hot-combustion gas suflicient to replace lieat; in the pyrolysis reaction; and lquerrching'fie gaseoustmixture flowingfromthe neacfionzone; i

3. 'Ihegprocessafor cumin. ously 0 the yr lys sot alinhat c-hydme rh mfi2A0 ..6. :.car-

ho atoms vwhich n membe hesr nm nsisfing n alkanes and olefins, .which comprisesmixingthe aliphatic much smaller concentrations of oxides of carbon. Thus, hy r carbon with ahot combustion gas which is cornthe process of this inventigngiyeshigh-yields of acetylene" and-greatiyreducefth'loss of hydrocarbon feed due to the formation of oxides of carbon by reaction with steam and the like.

It will be understood that the accompanying drawings and the foregoing examples are given solely for illustrative purposes and that this invention is not limited to the specific apparatus shown in the drawings or the specific embodiments described in the examples. On the other hand, it will be readily apparent to those skilled in the 75 more than 250 pletely formed in acombustion zone bythe combustion of a combustile gas and about a. stoichiometrlcal proportion of oxygen, continuously passing memixmre through an elongated tubularreaction .zone while maintaining the temperature of the gaseous mixture at the exit of the reaction zone at a temperature of from about 1100" C. to about 1300 C. and maintaining the temperature of the gaseous mixture throughout the length of the reaction zone at from about 1200 C. to about 1500" C. but not C. above the exit temperature by employing an initial amount of the combustion gas suflicient to provide a mixture at the entrance to the reaction zone having a temperature within the last mentioned temperature range and introducing into the reaction zone at a plurality of spaced points intermediate its length additional amounts of said hot combustion gas sulficient to replace heat consumed in the pyrolysis reaction, and quenching the gaseous mixture flowing from the reaction zone.

4. The process for continuously forming acetylene by the pyrolysis of an aliphatic hydrocarbon of 2 to 6 carbon atoms which is a member of the group consisting of alkanes and olefins, which comprises mixing the aliphatic hydrocarbon with a hot combustion gas having a temperature of from about 2000 C. to about 2200 C. which is completely formed in a combustion zone by the combustion of a combustible gas and about a stoichiometrical proportion of oxygen, continuously passing the mixture through an elongated tubular reaction zone while maintaining the temperature of the gaseous mixture at the exit of the reaction zone at a temperature of about 1300 C. and maintaining the temperature of the gaseous mixture throughout the length of the reaction zone at from about 1300 C. to about 1500" C. by employing an initial amount of the combustion gas suflicient to provide a mixture at the entrance to the reaction zone having a temperature of about 1500" C. and introducing into the reaction zone at a plurality of spaced points intermediate its length additional amounts of said hot combustion gas sutficient at each point to raise the temperature of the mixture to about 1500 C., and quenching the gaseous mixture flowing from the reaction zone.

5. The process for continuously forming acetylene by the pyrolysis of an aliphatic hydrocarbon of 1 to 6 carbon atoms which is a member of the group consisting of alkanes and olefins in an elongated reaction tube constructed of heat conductive, refractory material which also forms the inner wall of an elongated annular combustion zone, which process comprises continuously forming a hot combustion gas in the combustion zone by the complete combustion of a mixture of a combustible gas and about a stoichiometrical proportion of oxygen while flowing such mixture through said combustion zone from near the exit end of said reaction tube toward the inlet end of the tube, mixing the hot combustion gas with said aliphatic hydrocarbon near the inlet end of said tube and continuously passing the resulting mixture through said reaction tube from the inlet end to the exit end of said tube, the combustion gas being formed at a rate suflicient to maintain the gaseous mixture at the exit end of the reaction tube at a temperature of from about 1000 C. to about 1600" C. and to maintain the temperature of the gaseous mixture throughout the length of the reaction tube at from 800 C. to not more than 250 C. above the exit temperature, and quenching the gaseous mixture flowing from the exit end of the reaction tube.

6. The process for continuously forming acetylene by the pyrolysis of an aliphatic hydrocarbon of l to 6 carbon atoms which is a member of the group consisting of alkanes and olefins in an elongated reaction tube constructed of heat conductive, refractory material which also forms the inner Wall of an elongated annular combustion zone, which process comprises continuously forming a hot combustion gas in the combustion zone by the complete combustion of a mixture of a combustible gas and about a stoichiometrical proportion of oxygen while flowing such mixture through said combustion zone from near the exit end of said reaction tube toward the inlet end of the tube, mixing the hot combustion gas with said aliphatic hydrocarbon near the inlet end of said tube and continuously passing the resulting mixture through said reaction tube from the inlet end to the exit end of said tube, the combustion gas being formed at a rate sufficient to provide the heat necessary to form an initial mixture with the aliphatic hydrocarbon having a temperature of at least 800 C. but not more than the exit temperature, to pyrolyze the hydrocarbon, and to yield an exit temperature of from about 1100 C. to about 1400 C., and quenching the gaseous mixture flowing from the exit end of the reaction tube.

7. The process for continuously forming acetylene by the pyrolysis of an aliphatic hydrocarbon of 2 to 6 carbon atoms which is a member of the group consisting of allranes and olefins in an elongated reaction tube constructed of heat conductive, refractory material which also forms the inner wall of an elongated annular combustion zone, which process comprises continuously forming a hot combustion gas in the combustion zone by the complete combustion of a mixture of a combustible gas and about a stoichiometrical proportion of oxygen while flowing such mixture through said combustion zone froni'near the exit end of said reaction tube toward the inlet end of the tube, mixing the hot combustion gas with said aliphatic hydrocarbon near the inlet end of said tube and continuously passing the resulting mixture through said reaction tube from the inlet end to the exit end of said tube, the combustion gas being formed at a rate suflicient to provide the heat necessary to form an initial mixture with the aliphatic hydrocarbon having a temperature of from 800 C. to about 1000" C. and to pyrolyze the hydrocarbon while raising the temperature of the mixture in the reaction tube to an exit temperature of from about 1100 C. to about 1200 C., and quenching the gaseous mixture flowing from the exit end of the reaction tube.

References Cited in the file of this patent UNITED STATES PATENTS 2,377,847 Allen et a1. June 12, 1945 2,520,149 Keeling Aug. 29, 1950 2,959,629 Lindahl Nov. 8, 1960 2,983,771 Begley May 9, 1961 2,985,698 Pechtold et a1. May 23, 1961 

1. THE PROCESS FOR CONTINUOUSLY FORMING ACETYLENE BY THE PYROLYSIS OF AN ALIPHATIC HYDROCARBON OF 1 TO 6 CARBON ATOMS WHICH IS A MEMBER OF THE GROUP CONSISTING FO ALKNES AND OLEFINS, WHICH COMPRISES MIXING THE ALIPHATIC HYDROCARBON WITH A HOT COMBUSTION GAS WHICH IS COMPLETELY FORMED IN A COMBUSTION ZONE BY THE COMBUSTION OF A COMBUSTIBLE GAS AND ABOUT A STOICHIOMETRICAL PROPORTION OF OXYGEN, CONTINUOUSLY PASSING THE MIXTURE THROUGH AN ELONGATED TUBULAR REACTION ZONE WHILE MAINTAINING THE TEMPERATURE OF THE GASEOUS MIXTURE AT THE EXIT OF THE REACTION ZOE AT A TEMPERATURE OF FROM ABOUT 1000*C. TO ABOUT 1600*C. AND MAINTAINING THE TEMPERATURE OF THE GASEOUS MIXTURE THROUGHOUT THE LENGTH OF THE REACTION ZONE AT FROM 800*C. TO NOT MORE THAN 250*C. ABOVE THE EXIT TEMPERATURE BY EMPLOYING AN INITIAL AMOUNT OF THE COMBUSTION GAS SUFFICIENT TO PROVIDE A MIXTURE AT THE ENTRANCE TO THE REACTION ZONE HAVING A TEMPERATURE WITHIN THE LAST MENTIONED TEMPERATURE RANGE AND SUPPLYING ADDITINAL HEAT TO THE GASEOUS MIXTURE INTERMEDIATE THE LENGTH OF THE REACTION ZONE TO REPLACE HEAT CONSUMED IN THE PYROLYSIS REACTION, AND QUENCHING THE GASEOUS MIXTURE FLOWING FROM THE REACTION ZONE. 